There are various forms of pedal cycle. One, conventional, form of pedal cycle is that which is only ever driven by a cyclist applying force to the pedals thereof, such cycles sometimes being referred to as “push bikes”. Another, more recent, form of pedal cycle is the electrically-assisted pedal cycle (EAPC) in which electrical power is used to assist the efforts of a cyclist pedalling the cycle. Both conventional pedal cycles and EAPCs may have two, three or four wheels, and, in some, cases even more. In the present document, the term “pedal cycle” is used to include both conventional pedal cycles and EAPCs.
As mentioned, in an EAPC, electrical power is used to assist the efforts of a cyclist pedalling the cycle. Accordingly, EAPCs include means for storing electrical energy, such a batteries, and an electric motor arranged to propel, or at least assist in propelling, the cycle. The batteries can usually be recharged by plugging them into a supply of electrical energy, such as an outlet from a mains supply, and also by recovering energy from motion of the cycle by way of regenerative braking. The principle of regenerative braking will be familiar to those skilled in this field of technology. As a result, the overall effort required by a cyclist to pedal an EAPC is lower than for a conventional cycle.
EAPCs can usually be placed into one of two groups. The first group is that in which the cycle can provide electrical assistance on demand, at any time, regardless of whether or not the cyclist is pedalling. Cycles in this group are sometimes referred to as “e-bikes”, and can be thought of as being generally equivalent to electric mopeds, although one that is generally easier to pedal. Cycles in the second group only provide electrical assistance when the cyclist is pedalling. These are sometimes referred to as “pedelecs”.
In most European countries, pedelecs at least are effectively classified as conventional bicycles and so may be ridden without a driving license or insurance. In at least the UK, e-bikes are also classified in this way. There are therefore few barriers to owning and operating an EAPC.
In recent years, technical advances have been made to the electro-mechanical drive arrangements and to the associated energy storage and recovery devices used in EAPCs. These advances have resulted in EAPCs that can be operated with greater efficiency, and hence greater ease, by the cyclist.
For all the reasons given above EAPCs are becoming increasing popular, particularly in some European countries.
A suitable electro-mechanical drive arrangement for driving an EAPC is described in WO-A1-2006/035215, the contents of which are herein incorporated in their entirety. For example, this earlier document describes, with reference to FIG. 2 thereof, an arrangement that can be mounted to replace the conventional hub of a rear wheel of a bicycle. The replacement hub contains first and second motor-generators and first and second epicyclic gear sets. The arrangement is such that the motor-generators and the epicyclic gear sets operate to provide a compact drive arrangement combining (a) a variable transmission ratio between the input from the cyclist and the output to the driving wheel, with (b) electrical assistance.
Although various drive arrangements exist for EAPCs, including that described in WO-A1-2006/035215, the unpredictable nature of how a cyclist will cycle makes control and operation of such arrangements problematic. In this respect, a cyclist is very different from an engine.
An object of at least certain embodiments of this invention is to provide a method of operating an electro-mechanical drive arrangement for a pedal cycle similar to that described in WO-A1-2006/035215.